This invention relates to processing apparatus.
This invention has particular but not exclusive application to processing apparatus for opening hard shelled nuts and in particular macadamia nuts and for illustrative purposes references will be made to such application. However, it is to be understood that this invention could be used in other applications, such as for opening coconut shells.
Nuts such as macadamia nuts have a hard shell about a relatively fragile kernel. The value of the processed nut kernel is increased if clean whole nuts result are obtained from the removal process. While part kernels are retained for sale the value of half kernels is greater than that of broken kernels.
Macadamia nut shells are generally spherical but vary in shape and size and are frequently dried prior to opening so as to free the kernel from the shell with a view to recovering whole kernels. The drying process which occurs over several days is costly and causes extreme hardness of the shell.
The presently available automated cracking and separating apparatus tends to produce a high proportion of damaged kernels and results in the harvested kernels being contaminated by fragmented shell particles which may be contaminated by contact with the ground surrounding the trees, as organic fertilizers are often used to fertilise the trees.
U.S. Pat. No. 4,467,711 describes a method of and apparatus for cracking nuts utilising a conveyor elevating nuts at fixed spacing to a nut gripping and cracking apparatus. The conveyor comprises slats with openings to receive a nut and a support beneath the nut. The conveyed nuts pass to a cracking apparatus having respective blades which are brought together by hydraulic pressure to cause the blades to split the nut. A blade position sensing device limits blade travel after the nut is split.
Such apparatus has several disadvantages. Firstly, splitting of the nuts by compression between the blades results in brittle failure of the nut shell, resulting in a highly energetic shock. This tends to shatter the nut and the kernel. The shattered nut produces contamination of the kernel and especially when the kernel is also shattered by the splitting apparatus.
The apparatus is also limited in its line speed, and is therefor arranged in multiple assemblies to provide commercial throughput. One major limitation on the line speed is the stepwise nature of the method, requiring the nut to stop at the cutting station, introducing inertial delays and causing further damage to the kernels.
The present invention aims to alleviate at least one of the foregoing disadvantages and to provide nut processing apparatus which will be reliable and efficient in use.